Application to Membrane Separation Process

In natural gas, methane is the main component, and other hydrocarbons such as ethane, propane and butane may be present in smaller quantities. Water, H2S and CO2 are also present as impurities in natural gas, and they have to be removed before pumping the natural gas through pipelines. An amine absorption process is commonly used for removing these impurities. Nowadays, membranes are being explored for natural gas processing (Baker and Lokhandwala, 2008 Ahmad et al, 2012 Niu and Rangaiah, 2014). This section presents simulation and optimization of such a membrane separation process for two objectives, using Aspen Plus, ACM, I-MODE and interface between Aspen Plus and Excel. As mentioned earlier, chemical processes can be simulated in Aspen Plus. In Section 4.3, a membrane model has been implemented in ACM, which can be added to Aspen Plus. 

In this membrane separation process, CH4 recovery and CH4 purity are two important and conflicting objectives [see Equations (4.13) and (4.14)], and also they are free from fluctuating costs. The area of membrane in each stage is selected as the decision variable. 

Molar flow rate of CH4 in fresh feed Molar flow rate of CH4 in product stream Molar flow rate of product stream 

The I-MODE program of Sharma and Rangaiah (2013b) has been used to optimize the gas separation process for two objectives. It has taboo list, termination criterion and selfadaptation of algorithm parameters. In this study, a taboo radius of 0.01 and population size of 100 are used, and search is terminated based on the maximum number of generations (MNG = 100). The I-MODE program in Excel is interfaced with Aspen Plus via VBA (Section 4.5). 

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The investigation of Dean vortices and their application to membrane separation processes has been the subject of several experimental and theoretical studies concerning the improvement of microfiltration (ME), ultrafiltration (UF), and nanofiltration (NF),... 

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